For decades, women suffering from the most severe form of pregnancy sickness were often told their symptoms were psychological or simply a “rough patch” of early motherhood. But a massive international effort has now provided the most definitive biological evidence to date that the condition is rooted in genetics, uncovering six previously unknown genetic links to pregnancy sickness.
The study, published in Nature Genetics, focused on hyperemesis gravidarum (HG), a debilitating condition that affects approximately 2% of pregnancies. Unlike typical morning sickness, HG causes nausea and vomiting so profound that eating becomes nearly impossible, often leading to severe malnourishment and requiring hospitalization to protect both the mother and the fetus.
Led by Dr. Marlena Fejzo of the Keck School of Medicine of USC, the research represents the largest genetic analysis of HG ever conducted. Researchers analyzed data from 10,974 women diagnosed with the condition and 461,461 control subjects. To ensure the findings were applicable to a global population, the team included women of European, Asian, African, and Latino ancestries.
“Because this is the largest study of HG ever conducted, we’ve been able to tease out important new details that were previously unknown,” said Fejzo, a clinical assistant professor of population and public health sciences. She noted that the multi-ancestry approach suggests these results are generalizable across a broad range of populations.
The GDF15 Hormone and the ‘Sensitivity’ Trigger
Whereas the study identified 10 genes linked to HG, the most significant driver remains growth differentiation factor 15 (GDF15). This gene produces a hormone that naturally spikes during pregnancy, but the researchers found that the severity of a woman’s symptoms depends on her pre-pregnancy sensitivity to that hormone.
In a biological paradox, women who have naturally lower levels of GDF15 before becoming pregnant—often due to a specific genetic mutation—tend to experience the most severe symptoms when the hormone rises during pregnancy. Conversely, women who are exposed to higher levels of the hormone before pregnancy appear to be “desensitized” to it, resulting in milder nausea and vomiting.
This discovery shifts the understanding of HG from a random occurrence to a predictable biological response. By identifying the specific receptors and hormones involved, the research team has moved the conversation from managing symptoms to identifying the underlying cause.
Expanding the Genetic Map: Six New Discoveries
The new research more than doubles the number of genes associated with the condition. While four genes—GDF15, GFRAL (the GDF15 receptor), IGFBP7, and PGR—were already known to play a role in HG or placental development, the study identified six new genes: FSHB, TCF7L2, SLITRK1, SYN3, IGSF11, and CDH9.
Among these, TCF7L2 is particularly noteworthy. This proves already recognized as one of the strongest genetic risk factors for type 2 diabetes and is closely linked to gestational diabetes. Researchers believe TCF7L2 may influence glucagon-like peptide-1 (GLP-1), a gut hormone that regulates blood sugar and can trigger feelings of nausea and appetite suppression.
“This is a brand-new target, and it’s not yet clear what it’s doing in pregnancy,” Fejzo said.
Other newly identified genes are linked to brain plasticity—the way the brain adapts to new information. This suggests a neurological component to pregnancy sickness, where the brain may “learn” to associate specific foods with the feeling of illness, creating the intense and lasting food aversions common in HG patients.
Genetic Links and Pregnancy Complications
The study also revealed that the genetic markers for HG do not exist in isolation. Some of the genes linked to severe pregnancy sickness were also associated with other adverse pregnancy outcomes, including a shorter overall pregnancy length and an increased risk of preeclampsia, a dangerous high-blood-pressure condition.
| Gene Category | Key Genes | Biological Influence |
|---|---|---|
| Primary Driver | GDF15 / GFRAL | Hormonal sensitivity and receptor activation |
| Metabolic/Diabetes | TCF7L2 | GLP-1 influence, blood sugar, and appetite |
| Placental Development | IGFBP7 / PGR | Placenta formation and maintenance |
| Neurological | SYN3 / SLITRK1 | Brain plasticity and food aversion triggers |
Moving Toward Personalized Treatment
Current medical interventions for HG are often inadequate. Zofran, one of the most frequently prescribed medications, provides only partial relief for about half of the patients. The identification of these 10 genes opens the door to “precision medicine,” where treatments can be matched to a woman’s specific genetic profile.
The most immediate application of this research is a new clinical trial involving metformin, a common medication used to treat type 2 diabetes. Because metformin is known to increase GDF15 levels, researchers are testing whether taking the medication before pregnancy can desensitize women to the hormone. The goal is to prevent the onset of HG or reduce its severity in women who have suffered from it in previous pregnancies.
By treating the biological trigger before the pregnancy begins, doctors hope to eliminate the need for the emergency hospitalizations and intravenous feeding that currently characterize the most severe cases of HG.
Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.
The next milestone for this research will be the results of the metformin clinical trial, which aims to determine if prenatal hormonal desensitization is a viable preventative strategy for high-risk women.
Do you or a loved one have experience with hyperemesis gravidarum? Share your thoughts or questions in the comments below.
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